Rotary face seal failure caused by contamination of high precision sealing faces has long been a problem. Microscopic particles introduced prior to and during assembly into a shaft housing environment during either original production or in field service often results in face seal failures. Environmental conditions often permit dust, dirt, metal particles, etc. to adhere to the sealing faces prior to the final assembly and such contamination prevents full face area contact which allows a fluid leak path to form resulting in seal failure. Furthermore such particles may also become embedded causing surface scratches or scoring resulting in seal failure. Such possibility of contamination is even more of a problem in field service where a seal assembly must be replaced under extremely dirty conditions. This problem is increased by field service or repair of off-road equipment which is normally serviced in situ due to the expense of down time and because movement of a machine with leaky seals can cause contamination damage to other parts such as bearings.
Quite often the face seal elements are precision machined, in the example of the preferred embodiment of the present possession, to 0.000020 inch TIR and then cleaned and packaged in a clean room environment. Such efforts however are negated if the individual elements of the face seal and their retainer are individually assembled on a machine shaft in an assembly line environment or in a field service environment, neither of which begin to approach the contamination free environment of the clean room. This often results in the dust, dirt and even fingerprints contaminating the seal interface.
One apparatus and method of use utilized to reduce such face seal contamination is taught in U.S. Pat. Washington No. 3,947,944 issued Apr. 6, 1976 and Washington No. 4,026,005 issued May 31, 1977. The apparatus and method taught utilize a two-piece transfer fixture wherein the seal components are installed on such fixture in their appropriate working relationship with the seal faces maintained in an abutting relationship on a transfer fixture to prevent contamination of the face seal interface. Such abutment may be established in a clean room environment and maintained during subsequent handling until the face seal elements are positioned near their final assembly position. However, the two-piece transfer tool of these patents requires that the seal elements be removed from the transfer fixture and axially moved into their final assembly position. This last operation is without the aid of the transfer tool pilot which maintains concentricity and cleanliness. Due to manufacturing tolerances, there is no guarantee that the transfer tool pilot and the shaft are of equal diameter and thus it is possible that the desired special relationship between the elements of the face seal is not maintained during the last critical stage of the transfer operation unless each transfer tool pilot is machined to match the specific shaft diameter. Not only does this prior art structure not maintain the shaft seal assembly in its previous assembled form throughout the total transfer operation, but the shaft must be of a special shape to permit the transfer tool to be axially located near the final assembled position. An elongated constant diameter shaft would require an extreme stroke of the transfer tool thus limiting the practicality of the two-piece device.